One of the keys to building a good startup is taking advantage of luck, says Jack. In the case of Square his luck was the financial crisis. When the economy collapsed, Jack says it "allowed us to seek out the people we needed to talk to at the banks, at the government, at the card brands," because "they were in survival mode looking for innovation new business models."

This part of the talk starts around the 7:30 mark in the video below, but the whole thing is pretty entertaining and just 16 minutes.